Oscillator circuits are useful for providing a stable frequency for use in such devices as frequency filters and mixers.
In a paper by B. Linares-Barranco et al entitled "Very High Frequency CMOS OTA-C Quadrature Oscillators," published in Proc. IEEE/ISCAS 1990, International Symposium on Circuits and Systems, May 1-3, 1990, pp. 3189-3192, a block diagram of a quadrature oscillator was disclosed which included a triple-input integrator, one of the inputs being negative feedback from a single-input integrator. Another of its inputs included a positive-input path containing a clamp connected in series with an auxiliary amplifier.
The use of the clamp connected in series with the auxiliary amplifier introduces added circuitry which, in turn, undesirably dissipates power and lowers the cutoff frequency. Therefore, it would be desirable to have a quadrature oscillator without these disadvantages.